Object.keys()方法的常见用法

1.传入对象，返回对象的key值

var obj = new Object();
obj = {a:1,b:2};
console.log(Object.keys(obj)) //['a','b']

2.传入字符串，返回索引

var str = new String();
str = 'abc123';
console.log(Object.keys(str)); //['0','1','2','3','4','5']

3.构造函数 返回空数组或属性名

function Basic(name,age,address){
    this.name = name;
    this.age = age;
    this.address = address;
    this.info = function(){
        return (this.name + '/' + this.age + '/' + this.address);
    }
};
console.log(Object.keys(Basic)); //[]
var lily = new Basic('lily',22,'wuhan');
console.log(Object.keys(lily)); //['name','age','address','info']

4.数组 返回索引值

var arr = new Array();
arr = ['x','y','z'];
console.log(Object.keys(arr));//['0','1','2']